Apparatus for developing photolithographic plates

ABSTRACT

An apparatus for performing the developing sequence on exposed photolithographic plates wherein a photolithographic plate is advanced through the apparatus by a series of drive and nip rolls and wherein the plate is treated with a developing emulsion which is uniformly spread over the surface of the plate by a revolving developer bar, rinsed in a water wash and treated with a gumming solution by the action of an oscillating wiper sponge.

United States Patent [72] Inventors Paul Adams;

Ferdinand Lukasik, both of South Hadley, Mass. [211 App]. No. 772,543 [22] Filed Nov. 1, 1968 [45] Patented July 20, 1971 [73] Assignee John Stark Laboratories, Inc.

llolyoke, Mass.

[54] APPARATUS FOR DEVELOPING PHOTOLITHOGRAPHIC PLATES 9 Claims, 5 Drawing Figs.

[52] U.S.-Cl 95/89, 118/109, 118/111, 118/120 [51] lnt.Cl 603d 3/00 [50] Field of Search 95/89, 89 A, 94, 14; 1 18/100, 109, ll 1, 120,314,31'5,325

[56] References Cited UNITED STATES PATENTS 2,555,874 6/1951 Coughlin 95/89 2,677,320 5/ 1954 Coughlin 95/89 3,055,338 9/1962 Herzhoff et a1. 1 18/120 3,059,560 10/1962 Gutzmer 95/89 3,218,950 1 H1965 Liedl et al. 95/94 3,271,226 9/1966 Staehle et al. 95/89 X 3,338,149 9/1967 Hemery 95/89 3,354,807 11/1967 H0rner.... 95/89 X 3,448,720 6/1969 Graham 118/314 Primary Examiner--John M. Horan Assistant Examiner-Alan Matthews Attorney-Chapin, Neal and Dempsey APPARATUS FOR DEVELOPING PHOTOLITI'IOGRAPIIIC PLATES BACKGROUND The present invention relates to an apparatus for developing photolithographic plates or sheets. In particular it relates to an apparatus for developing offset photolithographic plates which are known in the trade as surface plates or negative form plates.

The process for producing negative form photolithographic plates may be basically described in seven steps: (I) Graining an aluminum sheet; (2) Treating the surface of the grained sheet to make it compatible-witha light sensitive coating; (3) Applying a light sensitive coatihg; to the sheet; (4) Exposing the sheet and image areas to lightto make the image areas insoluble; (5) Rubbing the entire surface of the exposed. plate with a developer emulsion which clears the background and raises the offset image; (6) Rinsing the surface of the sheet to remove excess developer emulsion; and (7) Wiping the sheet with a gumming solution such as asphaltum to cover nonprintmg areas.

At the-present time, the above-operations are primarily accomplished by handlabor. While-hand labor is somewhat effective, it is time consuming, ex-pensive and tendsto produce nonuniformly developed plates: The apparatus of the'present invention is mainly concerned" with the automation of steps (5) through (7) inclusive whichmay be generally referredto as the developing sequence.

Itis an object of. the present: invention to provide an apparatus which will replace thehandlabor mentioned above in regard to the developing sequence on photolithographic plates.

It is also an object of the present invention to provide an apparatus for automatically performing the developing sequence on photolithographic plates.

It is a further object of thisvinvention to provide an apparatus which will uniformly develop offset photolithographic plates. 1

Another object of the bleand sturdy. plates.

A still further'object of the present invention is to provide mechanical operating means formoving a developer bar uniformly of the entiresurface ofa photolithographicplate to be developed.

Theabove and other objects and advantages of the present invention will be apparent from ,the following specification with reference to'the accompanying drawings wherein,

FIG. I is a top plan view of the lithographic plate developer of thepresent invention;

FIG. 2 is a section view taken along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged partial section view taken alongthe line 3-3 of FIG. 1;

FIG. 4is a section view taken along the line 44 of FIG. I; and

FIG. 5 is a partial side view takenalong the line 5-5 of FIG. 4

present invention is to provide a reliaapparatus for developing photolithographic Referring to FIGS. 1 and 2 it vwill be seen that the lithographic plate developer of the presentinvention is indicated at 10. In general, it is comprised of abase portion 12 having a plurality of legs 14 depending therefrom.

The'base portion 12 supports asink or basin 16 which is formed by end walls 18, sidewalls-20 and a pitched bottom portion 22:'A drain 24 is disposed-at the lower end of the bottom portion 22 and a drain hose..26;is provided to carry off spentliquids which .will be further discussed below.

As further shown, a superstructure 28 is mounted on one side of the plate developer 10 andis-used to house and support various mechanical and electrical components of the apparatus.

Means; for. advancing the. plates; through the apparatus is provided by a plurality of feed or'drive rolls' 30, 32,i34 and. 36

which are laterally spaced throughout the length of the apparatus. Each of said rolls is joumaled within the basin 16 between the sidewalls 20. Nip rolls 38, 40, 42 and 44 are disposed above said drive rolls 30, 32, 34 and 36 respectively. Each of said nip rolls is provided with adjusting means 46 at each end thereof for varying the pressure against its corresponding feed roll. As shown, said adjusting means 46 comprises a bracket 48 mounted on a sidewall 20 and a collar 50, which rotatably supports an end of a nip roll. Said collar 50 is slidably disposed within said bracket 48 and is vertically movable by screw means 52 which is threaded into the top of the bracket 48.

Referring to feed rolls 30 and 32 and their corresponding nip rolls 38 and 40, respectively, it will be noted that their respective vertical center lines are ofiset. In particular, nip roll 38 is somewhat forward of feed roll 30, while nip roll 40 is somewhat behind feed roll 32. This positioning of the rolls tends to direct the leading edge of a lithographic plate, such as shown at 54, either downward as in the case of rolls 30 and 38 or upward as in the case of rolls 32 and 40.

As further illustrated, means for supporting the photolithographic plate or transfer plates 56, 58, and 60 are disposed between roll pairs. The transfer plates which are supported by brackets 62 on either side thereof are positioned so as to support and direct the litho plate 54 from the bite of one pair of rolls to the bite of the following pair of rolls.

Drive means for the feed rollsis provided by an electric motor 64 and power transmission means in operable connectionwith said motor 64 and said feed rolls 30, 32, 34 and 36. Typically such power transmission means may be a chain interconnecting sprockets (not shown) attached to said feed rolls and the electric motor 64. Of course, gear drive means and belt drive means are also contemplated.

Referring. to FIGS. 1, 2, 3 and 4, it will be seen that a developerhead 66 is located forward of the machine between nip rolls'38 and 40 above transfer plate 56 and perpendicular to the direction of travel of the plates through the apparatus. As shown, the head 66 comprises upper and lower cross members 68 and 70 respectively disposed 'on top of the sidewalls 20 and held in spaced relationship with one another by side members 72 and 74.

A developer bar or rubbing bar 76 which includes a sponge 78 or equivalent means afiixed to its underside is supported for revolving or gyrating operation by the developer head 66. The-means provided for general revolving operation of the developer bar comprises a power shaft 80 and support shafts 82 and 84 rotatably mounted in said developer head 66. As

I shown, each of said shafts has a counterweight eccentric 86 affixed to the lowermost end thereof. Offset shafts 88 depend from said eccentric 86 and are affixed to the developer bar 76. By this arrangement, rotary motion applied to the power shaft 80 by drive means, such as the pulleys 81 and 83, belt and power means (not shown) operably connected thereto, transmits a revolving motion to the developer bar 76 due to the offset relationship'between the shafts 80, 82 and 84 with shafts 88 provided by the counterweighted eccentrics 86.

The developer bar 76 is also provided with means for raising or lowering same. This is accomplished by a rack and pinion mechanism. With primary reference to FIG. 3 and the power shaft 80, it will be noted thatsaid shaft is mounted in the developer head 66 by means of a bushing 90. A sleeve 91 is slidably disposed within said bushing.90 and is provided with a rack plate 92 which extends outwardly through said bushing through slot 93 therein. The sleeve 91 'is' provided with upper and lower bearings (not shown) for rotatably receiving and centering the power shaft 80 and-' is held in position relative to said power 'shaft 80 by collars 94 and 96 which are pinned to the power shaft 80. The'su'pport shafts 82 and 84 are similarly supported.

As depicted, the rack plate-92 associated with each of the shafts 80, 82 and 84 has'a mating pinion 98. Each of the pinions 98 is attached by a pin or other suitable means to shaft 100 whichis joumaled in side members 72 and 74 of the developer head 66. Referring to FIGS. 1, 4 and 5 it will be noted that an end of shaft 100 extends beyond side plate 72 terminating in handle 102. Handle 102 is provided to axially raise and lower the developer bar by the action of the rack and pinion mechanism; A positioning plate 104 having holes 106 is also provided for maintaining the developer bar 76 at a predetermined distance in relation to the transfer plate 56.

Referring now to FIGS. 1, 2 and 3, it will be seen that means for applying a developer emulsion and a gumming solutionto photolithographic plates is also provided. The first of said means comprises a developer emulsion reservoir 110' for gravity feeding a developer emulsion into drip tube 112. The drip tube 112 which is disposed across the width of the apshutoff. Proximity, switch 114 also actuates the drive means for imparting motion tothe developer bar 76.

After the developer emulsion has been uniformly spread over the surface of the lithoplate 54 by the rotating motion of thedeveloper bar 76, it is necessary to remove any excess developer emulsion that is on the plate 54. This is accomplished by the plate passing in contact with sponge 116 which extends across the width of the apparatus on mounting bar 117 and a water wash provided by water drip tube 118 which is supplied from a standard tap (not shown). Flow of water in tube 118 may be manually controlled or actuated by proximity switch 114. g

The means for applying the gumming solution is provided by a second reservoir 120 which containsa gum arabic solution such as asphaltum. A gravity feed permits the solution to pass into drip tube 122 which is disposed across the width of the machine and drip control mechanisms 124 spaced throughout the length of the tube 122 allow the asphaltum to drip on the lithoplate being treated. Solenoid controlled valve means (not shown) for controlling the flow of solution from the reservoir 120 to the drip tube 122 is actuated by proximity switch 126. As in the case of the developer emulsion system, the duration of flow is preferably timed controlled.

Finally, a wiper bar 128 which includes a sponge 130 or equivalent means affixed thereto is disposed across the width of the machine perpendicular to the direction of travel of the 'plates' The bar 128 is affixed to mounting member 132 by shaftsl34 and said mounting member is slidably disposed in guideways 136 and 138 for oscillating motion provided by motor 140. The unit is actuated by a lithoplate contacting proximity switch 126.

Operation I The plate 54 which is being advanced by feed roll 30 and nip roll 38 is covered with thedeveloper emulsion before it passes into contact with the rubbing action of sponge 78 on the revolving developer bar 76. The action of the developer 1 bar uniformly rubs the developer solution all over the surface of the plate 54.

The plate 54 is then picked by drive roll 32 and nip roll 40 which push it into contact with sponge 116 where most of any excess developer emulsion is removed by the action of the sponge and a water rinse provided by watertube 118. Once the rear edged the plate 54 clears rolls 32 and 40, a time delay mechanism deactuates the motion of the developer bar therein for receiving a pin 108 extending from said handle 102 76 and the flow from drip tube 112. It should be noted, that in this particular operation the rinse solution falls into the sink or basin l6 and is drained from the apparatus via drain 24 and drain hose 26.

As the leading edge of the plate 54 clears the rear of sponge 116, it contacts proximity switch 126. The contact actuates flow of the gumming solution from the drip tube 122 and also actuates the oscillating wiping bar 128. As the lithoplate 54 passes under the drip tube 122 it is covered with the gumming solution. The oscillating action of sponge thoroughly spreads the solution over the entire surface of the plate 54.

Finally, the lithoplate 54 enters the bite of rolls 36 and 44 which passes it out of the apparatus. As the rear edge clears rolls 36 and 44 a time delay mechanism deactuates the wiper bar 128 and the flow of solution from drip tube 122.

' What we claim is:

l. An'apparatus for developing a photolithographic plate comprising in combination a first pair of rollers for initially advancing an exposed photolithographic plate into the apparatus, means for applying a developer emulsion to the exposed surface of said photolithographic plate, revolving means for uniformly distributing said developing emulsion evenly over the surface of said photolithographic plate including a developer head disposed above and perpendicular to the travel of said photolithographic plate through said apparatus and a developer bar supported for gyrating motion in contact with said photolithographic plate by said developer head, means for removing excess developer emulsion from said photolithographic plate, a second pair of rollers to remove said photolithographic platefrom the developing station and advance it to the excess developer removing station, means for supporting said photolithographic plate in said developing station disposed between said first and second pair of rollers, means for applying a gumming solution to said photolithographic plate, a third pair of rollers for transferring said photolithographic plate to the gumming station, means for supporting said photolithographic plate disposed between said second and third pair of rollers, an oscillating wiper bar for spreading said gumming solution uniformly on said photolithographic plate, a fourth pair of rollers for removal of the photolithographic plate from said apparatus and supporting means for said photolithographic plate disposed between the third and fourth pair of rollers.

'2. The apparatus of claim 1 wherein said means for applying the developer emulsion to said photolithographic plate includes a drip tube disposed across said apparatus perpendicular to the travel'of the photolithographic plate through said apparatus, a developer emulsion reservoir for supplying the developer emulsion to said drip tube, valve means for controlling the flow of said developer emulsion from said reservoir to said drip tube and switch means for actuating said valve means in response to the photolithographic plate traveling through said apparatus.

3. The apparatus of claim 1 wherein said means for applying the gumming solution to said photolithographic plate includes a drip tube disposed across said apparatus perpendicular to the travel of the photolithographic plate through the apparatus, a gumming solution reservoir for supplying the gumming solution to said drip tube, valve means for controlling the llow of said gumming solution from said reservoir to said drip tube, and switch means for actuating said valve means in response to the photolithographic plate traveling through said apparatus.

4. An apparatus for developing a photolithographic plate, comprising in combination a sink, a plurality of transfer plates for supporting said photolithographic plate over said sink, means for advancing said photolithographic plate through said apparatus, means for applying a developer emulsion to said photolithographic plate, a developer head disposed above one of said transfer plates and perpendicular to the travel of said photolithographic plate through said apparatus, said developer head including a plurality of support'shafts vertically disposed and rotatably mounted in said developer head,

a counterweight eccentric disposed on the lower end of each of said support shafts and a shaft depending from each of said counterweight eccentrics having their lower ends afiixed to said developer bar wherein said counterweight eccentrics provide an offset relationship between said support shafts and said shafts depending from said counterweight eccentrics whereby rotating motion of said support shafts transmits a revolving motion to said developer bar.

5. The apparatus of claim 4 wherein means for powering the developer bar includes an electric motor operably connected to at least one of said support shafts.

6. The apparatus of claim 4 wherein said developer head also includes means for raising and lowering the level of said developer bar relative to said developer head.

7. The apparatus of claim 6 wherein said means for raising and lowering the level of said developer bar includes a bushing for each of said support shafts having a vertical slot therein, a sleeve slidably mounted in each of said bushings for rotatably receiving and centering said support shaft, means for maintaining said sleeve in a single position relative to said support shaft, a rack disposed on said sleeve so as to extend into said slot in said bushing and a pinion engageable with each of said racks.

8. An apparatus for developing a photolithographic plate comprising in combination a sink, a plurality of feed and nip roll pairs disposed throughout the length of said apparatus above the bottom of said sink for advancing said plate through said apparatus, transfer plates disposed between said feed and nip roll pairs, means for applying a developer emulsion to said photolithographic plate, a revolving developer bar disposed across said apparatus for rubbing said developer emulsion uniformly on said photolithographic plate, means for powering said developer bar, a water wash for rinsing excess developer emulsion from said photolithographic plate, means for applying a gumming solution to said photolithographic plate, an oscillating wiper bar for uniformly spreading said gumming solution on said photolithographic plate and means for powering said oscillating wiper bar.

9. The apparatus of claim 8 which further includes a first switch for actuating said means for applying the developer emulsion to said photolithographic plate and for actuating said means for powering said developer bar, and a second switch for actuating said means for applying the gumming solution to said photolithographic plate and for actuating said means for powering said wiper bar, wherein said first switch and said second switch are in turn actuated by said photolithographic plate as said photolithographic plate travels through said apparatus. 

1. An apparatus for developing a photolithographic plate comprising in combination a first pair of rollers for initially advancing an exposed photolithographic plate into the apparatus, means for applying a developer emulsion to the exposed surface of said photolithographic plate, revolving means for uniformly distributing said developing emulsion evenly over the surface of said photolithographic plate including a developer head disposed above and perpendicular to the travel of said photolithographic plate through said apparatus and a developer bar supported for gyrating motion in contact with said photolithographic plate by said developer head, means for removing excess developer emulsion from said photolithographic plate, a second pair of rollers to remove said photolithographic plate from the developing station and advance it to the excess developer removing station, means for supporting said photolithographic plate in said developing station disposed between said first and second pair of rollers, means for applying a gumming solution to said photolithographic plate, a third pair of rollers for transferring said photolithographic plate to the gumming station, means for supporting said photolithographic plate disposed between said second and third pair of rollers, an oscillating wiper bar for spreading said gumming solution uniformly on said photolithographic plate, a fourth pair of rollers for removal of the photolithographic plate from said apparatus and supporting means for said photolithographic plate disposed between the third and fourth pair of rollers.
 2. The apparatus of claim 1 wherein said means for applying the developer emulsion to said photolithographic plate includes a drip tube disposed across said apparatus perpendicular to the travel of the photolithographic plate through said apparAtus, a developer emulsion reservoir for supplying the developer emulsion to said drip tube, valve means for controlling the flow of said developer emulsion from said reservoir to said drip tube and switch means for actuating said valve means in response to the photolithographic plate traveling through said apparatus.
 3. The apparatus of claim 1 wherein said means for applying the gumming solution to said photolithographic plate includes a drip tube disposed across said apparatus perpendicular to the travel of the photolithographic plate through the apparatus, a gumming solution reservoir for supplying the gumming solution to said drip tube, valve means for controlling the flow of said gumming solution from said reservoir to said drip tube, and switch means for actuating said valve means in response to the photolithographic plate traveling through said apparatus.
 4. An apparatus for developing a photolithographic plate, comprising in combination a sink, a plurality of transfer plates for supporting said photolithographic plate over said sink, means for advancing said photolithographic plate through said apparatus, means for applying a developer emulsion to said photolithographic plate, a developer head disposed above one of said transfer plates and perpendicular to the travel of said photolithographic plate through said apparatus, said developer head including a plurality of support shafts vertically disposed and rotatably mounted in said developer head, a counterweight eccentric disposed on the lower end of each of said support shafts and a shaft depending from each of said counterweight eccentrics having their lower ends affixed to said developer bar wherein said counterweight eccentrics provide an offset relationship between said support shafts and said shafts depending from said counterweight eccentrics whereby rotating motion of said support shafts transmits a revolving motion to said developer bar.
 5. The apparatus of claim 4 wherein means for powering the developer bar includes an electric motor operably connected to at least one of said support shafts.
 6. The apparatus of claim 4 wherein said developer head also includes means for raising and lowering the level of said developer bar relative to said developer head.
 7. The apparatus of claim 6 wherein said means for raising and lowering the level of said developer bar includes a bushing for each of said support shafts having a vertical slot therein, a sleeve slidably mounted in each of said bushings for rotatably receiving and centering said support shaft, means for maintaining said sleeve in a single position relative to said support shaft, a rack disposed on said sleeve so as to extend into said slot in said bushing and a pinion engageable with each of said racks.
 8. An apparatus for developing a photolithographic plate comprising in combination a sink, a plurality of feed and nip roll pairs disposed throughout the length of said apparatus above the bottom of said sink for advancing said plate through said apparatus, transfer plates disposed between said feed and nip roll pairs, means for applying a developer emulsion to said photolithographic plate, a revolving developer bar disposed across said apparatus for rubbing said developer emulsion uniformly on said photolithographic plate, means for powering said developer bar, a water wash for rinsing excess developer emulsion from said photolithographic plate, means for applying a gumming solution to said photolithographic plate, an oscillating wiper bar for uniformly spreading said gumming solution on said photolithographic plate and means for powering said oscillating wiper bar.
 9. The apparatus of claim 8 which further includes a first switch for actuating said means for applying the developer emulsion to said photolithographic plate and for actuating said means for powering said developer bar, and a second switch for actuating said means for applying the gumming solution to said photolithographic plate and for actuating said means for powering sAid wiper bar, wherein said first switch and said second switch are in turn actuated by said photolithographic plate as said photolithographic plate travels through said apparatus. 